There is some difference of opinion regarding the use of apostrophes in the pluralization of references to letters as symbols. New Fowler's Modern English Usage, after noting that the usage has changed, states at page 602 that "after letters an apostrophe is obligatory." The 15th edition of The Chicago Manual of Style states at paragraph 7.16, "To avoid confusion, lowercase letters ... form the plural with an apostrophe and an s". The Oxford Style Manual at page 116 advocates the use of common sense.

The third-person direct object pronouns o, os, a, and as, have variant forms prefixed with l- or n-. These alternative forms appear depending on the ending of the preceding word. The l- forms (e.g. los) are used when the preceding word ends in -r or -s. The n- forms (e.g. nos) are used when the preceding word ends in a -u or a diphthong. These alternative forms are then suffixed to the preceding word.

In all other situations, the standard forms of the pronouns are used (o, os, a, as) and are not suffixed to the preceding word.

These direct object pronouns also form contractions when they immediately follow an indirect object pronoun. For example, Dou che os ("I gave you them.") contracts to Dou chos.

Like other masculine Spanish words, masculine Spanish pronouns can be used when the gender of the subject is unknown or when the subject is plural and of mixed gender.1 Not used after con; conmigo, contigo, and consigo are used instead, respectively2 Use the third-person reflexive pronouns when appropriate3 Used only in Spain4 Depending on the implicit gender of the subject being referred to